Origin of the colossal permittivity of (Nb plus In) co-doped rutile ceramics by wide-range dielectric spectroscopy

0498094 - FZÚ 2019 RIV GB eng J - Journal Article
Petzelt, Jan - Nuzhnyy, Dmitry - Bovtun, Viktor - Crandles, D.A.
Origin of the colossal permittivity of (Nb plus In) co-doped rutile ceramics by wide-range dielectric spectroscopy.
Phase Transitions. Roč. 91, č. 9-10 (2018), s. 932-941. ISSN 0141-1594. E-ISSN 1029-0338
R&D Projects: GA ČR GA18-09265S; GA MŠMT EF16_019/0000760
Grant - others:OP VVV - SOLID21(XE) CZ.02.1.01/0.0/0.0/16_019/0000760
Institutional support: RVO:68378271
Keywords : dielectric spectroscopy * co-doped rutile ceramics * effective medium approximation * surface and internal barrier-layer capacitor effects
OECD category: Condensed matter physics (including formerly solid state physics, supercond.)
Impact factor: 1.026, year: 2018

Searching for giant dipolar defects, suggested as the explanation of the colossal permittivity (CP) in (Nb + In) co-doped rutile, we have recently published temperature-dependent dielectric spectra from sub-Hz to THz range (including 4-point DC conductivity) of several (Nb + In) co-doped rutile ceramics. Using the model of two leaky capacitor in series below ∼1 MHz, we estimated the depletion layer thickness and conductivity. The spectra below ∼10 GHz were fitted with two Cole–Cole relaxations obeying the Arrhenius law, assigned to the effect of depletion layers and grain boundaries. In this paper, using effective medium models, we have for the first time modelled the spectra as a composite of semiconducting grains and substantially less-conducting grain boundaries and near-electrode depletion layers. The CP effect has been fully explained by the combination of surface and internal barrier-layer capacitor effects, without any measurable contribution from the dipolar defects.

Permanent Link: http://hdl.handle.net/11104/0290513